# its me again -.- help with another exponential question? :D

• Mar 2nd 2013, 10:42 PM
pumbaa213
its me again -.- help with another exponential question? :D
Solve the following equation:

http://latex.codecogs.com/gif.latex?...+3}=2^{1-x}+15

I don't know what to do with the 15!!! (Headbang)

Thank you very much!!
• Mar 3rd 2013, 12:05 AM
chiro
Re: its me again -.- help with another exponential question? :D
Hey pumbaa213.

Apart from trial and error, you will probably have to use a root finding algorithm. Have you come across this in class?
• Mar 3rd 2013, 02:07 AM
ibdutt
Re: its me again -.- help with another exponential question? :D
• Mar 3rd 2013, 09:52 AM
Paze
Re: its me again -.- help with another exponential question? :D
Quote:

Originally Posted by ibdutt

Do you solve the last part with logarithms or have they not been taught when solving these? I just want to make sure I am not using anything that is ''not allowed''.
• Mar 3rd 2013, 10:21 AM
HallsofIvy
Re: its me again -.- help with another exponential question? :D
You don't need logarithms. It should be obvious that if \$\displaystyle 2^x= 2\$ then x= 1. (You do need to know that \$\displaystyle y= a^x\$, for a positive, is a "one-to-one function" to know that x= 1 is the only solution.
• Mar 3rd 2013, 10:48 AM
Paze
Re: its me again -.- help with another exponential question? :D
Quote:

Originally Posted by HallsofIvy
You don't need logarithms. It should be obvious that if \$\displaystyle 2^x= 2\$ then x= 1. (You do need to know that \$\displaystyle y= a^x\$, for a positive, is a "one-to-one function" to know that x= 1 is the only solution.

Okay, so we don't need logarithm until the answer becomes more complicated..Like x=2/3 or something. Right?
• Mar 3rd 2013, 11:53 AM
bjhopper
Re: its me again -.- help with another exponential question? :D
X is not equal to 1
2^4 is not equal to 0+15
If X = 0.9999 you get a close equality